tcp/quic lab patched

network/tcpquiclab/Makefile

@@ -2,7 +2,7 @@ CC = gcc
 CFLAGS = -Wall -g
 LDFLAGS = -lquiche -ldl -lpthread -lm
 
-all: tcp_server tcp_client quic_server quic_client tcp_perf_server tcp_perf_client quic_perf_server quic_perf_client
+all: tcp_server tcp_client quic_server quic_client tcp_perf_server tcp_perf_client quic_perf_server quic_perf_client tcp_multi_server tcp_multi_client quic_multi_server quic_multi_client
 
 tcp_server: tcp_server.c
 	$(CC) $(CFLAGS) -o tcp_server tcp_server.c
@@ -28,5 +28,17 @@ quic_perf_server: quic_perf_server.c
 quic_perf_client: quic_perf_client.c
 	$(CC) $(CFLAGS) -o quic_perf_client quic_perf_client.c $(LDFLAGS)
 
+tcp_multi_server: tcp_multi_server.c
+	$(CC) $(CFLAGS) -o tcp_multi_server tcp_multi_server.c -lpthread
+
+tcp_multi_client: tcp_multi_client.c
+	$(CC) $(CFLAGS) -o tcp_multi_client tcp_multi_client.c -lpthread
+
+quic_multi_server: quic_multi_server.c
+	$(CC) $(CFLAGS) -o quic_multi_server quic_multi_server.c $(LDFLAGS)
+
+quic_multi_client: quic_multi_client.c
+	$(CC) $(CFLAGS) -o quic_multi_client quic_multi_client.c $(LDFLAGS)
+
 clean:
-	rm -f tcp_server tcp_client quic_server quic_client tcp_perf_server tcp_perf_client quic_perf_server quic_perf_client
+	rm -f tcp_server tcp_client quic_server quic_client tcp_perf_server tcp_perf_client quic_perf_server quic_perf_client tcp_multi_server tcp_multi_client quic_multi_server quic_multi_client

network/tcpquiclab/README_LINUX.md

@@ -103,7 +103,38 @@ We use Linux `tc` (Traffic Control) with `netem` instead of `clumsy`.
    sudo tc qdisc del dev lo root
    ```
 
-### 3.3 & 3.4 Advanced Tests
+### 3.3 Advanced Test: Multiplexing vs Multi-Connection
 
-- **Multiplexing:** The current `quic_perf_client` uses a single stream (Stream ID 4). You can modify the code to launch multiple streams in parallel to test head-of-line blocking resilience.
+This task compares the performance of 5 parallel TCP connections against a single QUIC connection with 5 concurrent streams.
-- **Network Recovery:** Use `tc` to drop 100% packets (`loss 100%`) for 30 seconds during a long transfer, then remove the rule (`del`) to see if the connection recovers.
+
+**Scenario 1: TCP Multi-Connection**
+Establish 5 TCP connections simultaneously, each transferring 20MB (Total 100MB).
+
+1. Start TCP Multi-Connection Server:
+   ```bash
+   ./tcp_multi_server
+   ```
+2. Run TCP Multi-Connection Client:
+   ```bash
+   ./tcp_multi_client
+   ```
+3. Record total time and throughput from the server output.
+
+**Scenario 2: QUIC Single-Connection Multi-Streaming**
+Establish 1 QUIC connection and open 5 streams concurrently, each transferring 20MB (Total 100MB).
+
+1. Start QUIC Multi-Stream Server:
+   ```bash
+   ./quic_multi_server
+   ```
+2. Run QUIC Multi-Stream Client:
+   ```bash
+   ./quic_multi_client
+   ```
+3. Record the performance statistics.
+
+**Analysis Points:**
+- Compare completion times in a normal network.
+- Use `tc` to simulate packet loss (e.g., 5%). Observe how QUIC's multiplexing avoids TCP's Head-of-Line (HoL) blocking, where a single lost packet in one TCP connection doesn't stall the other streams in QUIC.
+
+### 3.4 Network Recovery

network/tcpquiclab/README_LINUX_CN.md

@@ -103,7 +103,38 @@ make
    sudo tc qdisc del dev lo root
    ```
 
-### 3.3 & 3.4 进阶测试
+### 3.3 进阶测试：多路复用与多连接对比
 
-- **多路复用：** 当前的 `quic_perf_client` 使用单个流 (Stream ID 4)。您可以修改代码并行启动多个流，以测试 QUIC 解决队头阻塞问题的能力。
+本实验任务要求对比 TCP 多连接与 QUIC 多流复用的性能。
-- **网络恢复：** 在长传输过程中，使用 `tc` 设置 100% 丢包 (`loss 100%`) 持续 30 秒，然后删除规则 (`del`)，观察连接是否能恢复传输。
+
+**场景 1: TCP 多连接并发**
+同时建立 5 个 TCP 连接，每个连接传输 20MB 数据 (总计 100MB)。
+
+1. 启动 TCP 多连接服务器：
+   ```bash
+   ./tcp_multi_server
+   ```
+2. 启动 TCP 多连接客户端：
+   ```bash
+   ./tcp_multi_client
+   ```
+3. 记录服务器输出的总时间与吞吐量。
+
+**场景 2: QUIC 单连接多流复用**
+建立 1 个 QUIC 连接，在其中同时开启 5 个流 (Stream)，每个流传输 20MB 数据 (总计 100MB)。
+
+1. 启动 QUIC 多流服务器：
+   ```bash
+   ./quic_multi_server
+   ```
+2. 启动 QUIC 多流客户端：
+   ```bash
+   ./quic_multi_client
+   ```
+3. 记录服务器输出的统计数据。
+
+**分析重点：**
+- 在正常网络下，两者的总耗时差异。
+- 使用 `tc` 模拟丢包 (如 5%) 后，对比两者性能下降的幅度。QUIC 的多流复用应能避免 TCP 的“队头阻塞”问题 (即一个包丢失不影响其他流的传输)，从而在丢包环境下表现更优。
+
+### 3.4 网络恢复测试

network/tcpquiclab/quic_multi_client.c

@@ -0,0 +1,169 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <quiche.h>
+#include <stdbool.h>
+
+#define MAX_DATAGRAM_SIZE 1350
+#define TOTAL_MB 100
+#define NUM_STREAMS 5
+#define MB_PER_STREAM (TOTAL_MB / NUM_STREAMS)
+
+typedef struct {
+    uint64_t stream_id;
+    long long bytes_sent;
+    long long bytes_total;
+    bool finished;
+} StreamState;
+
+int main(int argc, char *argv[]) {
+    quiche_config *config = quiche_config_new(QUICHE_PROTOCOL_VERSION);
+    if (config == NULL) return -1;
+    
+    quiche_config_verify_peer(config, false); 
+    quiche_config_set_application_protos(config, (uint8_t *) "\x0ahq-interop\x05hq-29\x05hq-28\x05hq-27\x08http/0.9", 38);
+    quiche_config_set_max_idle_timeout(config, 10000);
+    quiche_config_set_max_recv_udp_payload_size(config, MAX_DATAGRAM_SIZE);
+    quiche_config_set_max_send_udp_payload_size(config, MAX_DATAGRAM_SIZE);
+    quiche_config_set_initial_max_data(config, 1024 * 1024 * 500);
+    quiche_config_set_initial_max_stream_data_bidi_local(config, 1024 * 1024 * 100);
+    quiche_config_set_initial_max_stream_data_bidi_remote(config, 1024 * 1024 * 100);
+    quiche_config_set_initial_max_streams_bidi(config, 100);
+    quiche_config_set_cc_algorithm(config, QUICHE_CC_RENO);
+
+    int sock = socket(AF_INET, SOCK_DGRAM, 0);
+    if (sock < 0) return -1;
+    
+    struct sockaddr_in peer_addr;
+    memset(&peer_addr, 0, sizeof(peer_addr));
+    peer_addr.sin_family = AF_INET;
+    peer_addr.sin_port = htons(8889);
+    inet_pton(AF_INET, "100.115.45.1", &peer_addr.sin_addr);
+    
+    if (connect(sock, (struct sockaddr *)&peer_addr, sizeof(peer_addr)) < 0) return -1;
+    
+    struct sockaddr_in local_addr;
+    socklen_t local_addr_len = sizeof(local_addr);
+    if (getsockname(sock, (struct sockaddr *)&local_addr, &local_addr_len) < 0) return -1;
+
+    int flags = fcntl(sock, F_GETFL, 0);
+    fcntl(sock, F_SETFL, flags | O_NONBLOCK);
+    
+    uint8_t scid[QUICHE_MAX_CONN_ID_LEN];
+    int rng = open("/dev/urandom", O_RDONLY);
+    read(rng, scid, sizeof(scid));
+    close(rng);
+    
+    quiche_conn *conn = quiche_connect("100.115.45.1", (const uint8_t *)scid, sizeof(scid), (struct sockaddr *)&local_addr, local_addr_len, (struct sockaddr *)&peer_addr, sizeof(peer_addr), config);
+    if (conn == NULL) return -1;
+    
+    printf("Connecting to QUIC Multi-Stream Server...\n");
+    printf("Sending %d streams, %d MB each (Total %d MB)...\n", NUM_STREAMS, MB_PER_STREAM, TOTAL_MB);
+    
+    uint8_t buf[65535];
+    uint8_t out[MAX_DATAGRAM_SIZE];
+    uint8_t payload[4096];
+    memset(payload, 'C', sizeof(payload));
+
+    // Initialize stream states
+    StreamState streams[NUM_STREAMS];
+    for (int i = 0; i < NUM_STREAMS; i++) {
+        streams[i].stream_id = 4 * i + 4; // 4, 8, 12, 16, 20... (Client Bidi) or simple increment if library handles it? 
+        // Note: Client initiated bidi streams usually start at 0, then 4, 8... 
+        // but let's stick to explicit IDs or check quiche docs.
+        // Quiche expects us to use IDs. 0, 4, 8, 12, 16 are valid client bidi.
+        streams[i].stream_id = i * 4; 
+        streams[i].bytes_sent = 0;
+        streams[i].bytes_total = (long long)MB_PER_STREAM * 1024 * 1024;
+        streams[i].finished = false;
+    }
+
+    bool all_finished = false;
+
+    while (1) {
+        ssize_t read_len = recv(sock, buf, sizeof(buf), MSG_DONTWAIT);
+        if (read_len > 0) {
+             quiche_conn_recv(conn, buf, read_len, &(quiche_recv_info){
+                 .to = (struct sockaddr *)&local_addr,
+                 .to_len = local_addr_len,
+                 .from = (struct sockaddr *)&peer_addr,
+                 .from_len = sizeof(peer_addr),
+             });
+        }
+
+        if (quiche_conn_is_closed(conn)) {
+            printf("Connection closed.\n");
+            break;
+        }
+
+        if (quiche_conn_is_established(conn)) {
+             all_finished = true;
+             for (int i = 0; i < NUM_STREAMS; i++) {
+                 if (!streams[i].finished) {
+                     all_finished = false;
+                     // Try to send on this stream
+                     while (streams[i].bytes_sent < streams[i].bytes_total) {
+                         uint64_t err_code = 0;
+                         // Determine payload size
+                         ssize_t sent = quiche_conn_stream_send(conn, streams[i].stream_id, payload, sizeof(payload), false, &err_code);
+                         if (sent > 0) {
+                             streams[i].bytes_sent += sent;
+                             if (streams[i].bytes_sent >= streams[i].bytes_total) {
+                                 // Send FIN
+                                 quiche_conn_stream_send(conn, streams[i].stream_id, NULL, 0, true, &err_code);
+                                 streams[i].finished = true;
+                                 printf("Stream %ld finished.\n", streams[i].stream_id);
+                             }
+                         } else {
+                             // E.g. Done (congestion) or Stream Limit
+                             break; 
+                         }
+                     }
+                 }
+             }
+
+             if (all_finished) {
+                 // Wait a bit to ensure ACKs or just exit?
+                 // Ideally wait for close, but let's just loop a bit or wait for idle.
+                 // Actually the server will likely not close connection, we can just idle.
+             }
+        }
+
+        bool has_outgoing = false;
+        while (1) {
+            quiche_send_info send_info;
+            ssize_t written = quiche_conn_send(conn, out, sizeof(out), &send_info);
+            if (written == QUICHE_ERR_DONE) break;
+            if (written < 0) break;
+            send(sock, out, written, 0);
+            has_outgoing = true;
+        }
+
+        quiche_conn_on_timeout(conn);
+        if (!has_outgoing && !all_finished) usleep(100);
+        if (all_finished && !has_outgoing) {
+             // Maybe wait for connection close or timeout
+             usleep(100000); // Wait 100ms
+             // quiche_conn_close(conn, true, 0, "Done", 4);
+             // break;
+             // Let's keep it alive for a moment for server to ack then exit
+             static int linger = 0;
+             if (linger++ > 20) {
+                 printf("All streams finished. Closing.\n");
+                 uint8_t reason[] = "done";
+                 quiche_conn_close(conn, true, 0, reason, sizeof(reason));
+                 break; 
+             }
+        }
+    }
+
+    quiche_conn_free(conn);
+    quiche_config_free(config);
+    return 0;
+}

network/tcpquiclab/quic_multi_server.c

@@ -0,0 +1,179 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <quiche.h>
+#include <time.h>
+
+#define MAX_DATAGRAM_SIZE 1350
+#define LOCAL_CONN_ID_LEN 16
+#define TARGET_MB 100 // Target total MB to receive
+
+typedef struct {
+    int sock;
+    struct sockaddr_storage peer_addr;
+    socklen_t peer_addr_len;
+    quiche_conn *conn;
+    long long total_bytes;
+    struct timespec start_time;
+    int timer_started;
+} Client;
+
+int main(int argc, char *argv[]) {
+    quiche_config *config = quiche_config_new(QUICHE_PROTOCOL_VERSION);
+    if (config == NULL) return -1;
+
+    quiche_config_load_cert_chain_from_pem_file(config, "cert.crt");
+    quiche_config_load_priv_key_from_pem_file(config, "cert.key");
+    
+    quiche_config_set_application_protos(config, (uint8_t *) "\x0ahq-interop\x05hq-29\x05hq-28\x05hq-27\x08http/0.9", 38);
+    quiche_config_set_max_idle_timeout(config, 10000);
+    quiche_config_set_max_recv_udp_payload_size(config, MAX_DATAGRAM_SIZE);
+    quiche_config_set_max_send_udp_payload_size(config, MAX_DATAGRAM_SIZE);
+    quiche_config_set_initial_max_data(config, 1024 * 1024 * 500);
+    quiche_config_set_initial_max_stream_data_bidi_local(config, 1024 * 1024 * 100);
+    quiche_config_set_initial_max_stream_data_bidi_remote(config, 1024 * 1024 * 100);
+    quiche_config_set_initial_max_streams_bidi(config, 100);
+    quiche_config_set_cc_algorithm(config, QUICHE_CC_RENO);
+
+    struct sockaddr_in sa;
+    memset(&sa, 0, sizeof(sa));
+    sa.sin_family = AF_INET;
+    sa.sin_port = htons(8889);
+    sa.sin_addr.s_addr = INADDR_ANY;
+
+    int sock = socket(AF_INET, SOCK_DGRAM, 0);
+    if (sock < 0) return -1;
+    if (bind(sock, (struct sockaddr *)&sa, sizeof(sa)) < 0) return -1;
+
+    int flags = fcntl(sock, F_GETFL, 0);
+    fcntl(sock, F_SETFL, flags | O_NONBLOCK);
+
+    printf("QUIC Multi-Stream Server listening on port 8889\n");
+    printf("Expecting approx %d MB total data...\n", TARGET_MB);
+
+    Client *client = NULL; 
+    uint8_t buf[65535];
+    uint8_t out[MAX_DATAGRAM_SIZE];
+    bool done_printing = false;
+
+    while (1) {
+        struct sockaddr_storage peer_addr;
+        socklen_t peer_addr_len = sizeof(peer_addr);
+        ssize_t read_len = recvfrom(sock, buf, sizeof(buf), 0, (struct sockaddr *)&peer_addr, &peer_addr_len);
+
+        if (read_len > 0) {
+            uint8_t type;
+            uint32_t version;
+            uint8_t scid[QUICHE_MAX_CONN_ID_LEN];
+            size_t scid_len = sizeof(scid);
+            uint8_t dcid[QUICHE_MAX_CONN_ID_LEN];
+            size_t dcid_len = sizeof(dcid);
+            uint8_t token[256];
+            size_t token_len = sizeof(token);
+
+            int rc = quiche_header_info(buf, read_len, LOCAL_CONN_ID_LEN, &version, &type, scid, &scid_len, dcid, &dcid_len, token, &token_len);
+
+            if (rc >= 0) {
+                if (client == NULL) {
+                    if (!quiche_version_is_supported(version)) {
+                         ssize_t written = quiche_negotiate_version(scid, scid_len, dcid, dcid_len, out, sizeof(out));
+                         if (written > 0) sendto(sock, out, written, 0, (struct sockaddr *)&peer_addr, peer_addr_len);
+                    } else {
+                         client = malloc(sizeof(Client));
+                         client->sock = sock;
+                         client->peer_addr = peer_addr;
+                         client->peer_addr_len = peer_addr_len;
+
+                         uint8_t server_scid[QUICHE_MAX_CONN_ID_LEN];
+                         int rng = open("/dev/urandom", O_RDONLY);
+                         read(rng, server_scid, sizeof(server_scid));
+                         close(rng);
+
+                         client->conn = quiche_accept(server_scid, sizeof(server_scid), dcid, dcid_len, (struct sockaddr *)&sa, sizeof(sa), (struct sockaddr *)&peer_addr, peer_addr_len, config);
+                         client->total_bytes = 0;
+                         client->timer_started = 0;
+                         printf("Connection accepted.\n");
+                    }
+                }
+
+                if (client != NULL) {
+                    quiche_conn_recv(client->conn, buf, read_len, &(quiche_recv_info){
+                        .to = (struct sockaddr *)&sa,
+                        .to_len = sizeof(sa),
+                        .from = (struct sockaddr *)&peer_addr,
+                        .from_len = peer_addr_len,
+                    });
+                }
+            }
+        }
+
+        if (client != NULL) {
+            quiche_conn *conn = client->conn;
+
+            if (quiche_conn_is_closed(conn)) {
+                printf("Connection closed.\n");
+                free(client);
+                client = NULL;
+                break;
+            }
+
+            if (quiche_conn_is_established(conn)) {
+                uint64_t s = 0;
+                quiche_stream_iter *readable = quiche_conn_readable(conn);
+                while (quiche_stream_iter_next(readable, &s)) {
+                    if (!client->timer_started) {
+                        clock_gettime(CLOCK_MONOTONIC, &client->start_time);
+                        client->timer_started = 1;
+                    }
+
+                    uint8_t recv_buf[65535];
+                    bool fin = false;
+                    uint64_t err_code = 0;
+                    ssize_t recv_bytes = quiche_conn_stream_recv(conn, s, recv_buf, sizeof(recv_buf), &fin, &err_code);
+                    if (recv_bytes > 0) {
+                        client->total_bytes += recv_bytes;
+                    }
+                }
+                quiche_stream_iter_free(readable);
+                
+                // Check if target reached (fuzzy check as logic overhead might mean exact bytes vary slightly or we just use >=)
+                if (client->total_bytes >= (long long)TARGET_MB * 1024 * 1024 && !done_printing) {
+                        struct timespec end;
+                        clock_gettime(CLOCK_MONOTONIC, &end);
+                        double time_taken = (end.tv_sec - client->start_time.tv_sec) + (end.tv_nsec - client->start_time.tv_nsec) / 1e9;
+                        double mb = client->total_bytes / (1024.0 * 1024.0);
+                        double throughput = mb / time_taken;
+
+                        printf("\nTest Finished:\n");
+                        printf("Total Data Received: %.2f MB\n", mb);
+                        printf("Time Taken: %.2f seconds\n", time_taken);
+                        printf("Total Throughput: %.2f MB/s\n", throughput);
+                        done_printing = true;
+                }
+            }
+
+            bool has_outgoing = false;
+            while (1) {
+                quiche_send_info send_info;
+                ssize_t written = quiche_conn_send(conn, out, sizeof(out), &send_info);
+                if (written == QUICHE_ERR_DONE) break;
+                if (written < 0) break;
+                sendto(sock, out, written, 0, (struct sockaddr *)&send_info.to, send_info.to_len);
+                has_outgoing = true;
+            }
+
+            quiche_conn_on_timeout(conn);
+            if (!has_outgoing && !done_printing) usleep(100); 
+            if (done_printing && !has_outgoing) usleep(10000); // Slow down if done
+        }
+    }
+    
+    quiche_config_free(config);
+    return 0;
+}

network/tcpquiclab/tcp_multi_client.c

@@ -0,0 +1,70 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <arpa/inet.h>
+#include <sys/socket.h>
+#include <pthread.h>
+
+#define PORT 8081
+#define SERVER_IP "100.115.45.1" // Default IP, change if needed
+#define BUFFER_SIZE 4096
+#define TOTAL_MB 100
+#define NUM_CONNS 5
+#define MB_PER_CONN (TOTAL_MB / NUM_CONNS)
+
+void *send_data(void *arg) {
+    int sock = 0;
+    struct sockaddr_in serv_addr;
+    char buffer[BUFFER_SIZE];
+    memset(buffer, 'B', BUFFER_SIZE);
+
+    if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
+        printf("\n Socket creation error \n");
+        return NULL;
+    }
+
+    serv_addr.sin_family = AF_INET;
+    serv_addr.sin_port = htons(PORT);
+
+    if (inet_pton(AF_INET, SERVER_IP, &serv_addr.sin_addr) <= 0) {
+        printf("\nInvalid address/ Address not supported \n");
+        return NULL;
+    }
+
+    if (connect(sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
+        printf("\nConnection Failed \n");
+        return NULL;
+    }
+
+    long long bytes_to_send = (long long)MB_PER_CONN * 1024 * 1024;
+    long long bytes_sent = 0;
+
+    while (bytes_sent < bytes_to_send) {
+        int to_send = (bytes_to_send - bytes_sent > BUFFER_SIZE) ? BUFFER_SIZE : (bytes_to_send - bytes_sent);
+        send(sock, buffer, to_send, 0);
+        bytes_sent += to_send;
+    }
+
+    close(sock);
+    return NULL;
+}
+
+int main(int argc, char const *argv[]) {
+    pthread_t threads[NUM_CONNS];
+    printf("Starting %d TCP connections, sending %d MB each (Total %d MB).\n", NUM_CONNS, MB_PER_CONN, TOTAL_MB);
+
+    for (int i = 0; i < NUM_CONNS; i++) {
+        if (pthread_create(&threads[i], NULL, send_data, NULL) != 0) {
+            perror("Thread create failed");
+            return 1;
+        }
+    }
+
+    for (int i = 0; i < NUM_CONNS; i++) {
+        pthread_join(threads[i], NULL);
+    }
+
+    printf("All connections finished sending.\n");
+    return 0;
+}

network/tcpquiclab/tcp_multi_server.c

@@ -0,0 +1,118 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <arpa/inet.h>
+#include <sys/socket.h>
+#include <pthread.h>
+#include <time.h>
+
+#define PORT 8081
+#define BUFFER_SIZE 4096
+#define EXPECTED_CONNECTIONS 5
+#define TOTAL_TARGET_MB 100
+
+long long global_bytes_received = 0;
+int connections_handled = 0;
+pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
+struct timespec start_time, end_time;
+int first_connect = 1;
+
+void *handle_client(void *socket_desc) {
+    int sock = *(int*)socket_desc;
+    free(socket_desc);
+    char buffer[BUFFER_SIZE];
+    int valread;
+    long long thread_bytes = 0;
+
+    while ((valread = read(sock, buffer, BUFFER_SIZE)) > 0) {
+        thread_bytes += valread;
+    }
+
+    pthread_mutex_lock(&lock);
+    global_bytes_received += thread_bytes;
+    connections_handled++;
+    pthread_mutex_unlock(&lock);
+
+    close(sock);
+    return NULL;
+}
+
+int main() {
+    int server_fd, new_socket;
+    struct sockaddr_in address;
+    int opt = 1;
+    int addrlen = sizeof(address);
+
+    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {
+        perror("socket failed");
+        exit(EXIT_FAILURE);
+    }
+
+    if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, &opt, sizeof(opt))) {
+        perror("setsockopt");
+        exit(EXIT_FAILURE);
+    }
+
+    address.sin_family = AF_INET;
+    address.sin_addr.s_addr = INADDR_ANY;
+    address.sin_port = htons(PORT);
+
+    if (bind(server_fd, (struct sockaddr *)&address, sizeof(address)) < 0) {
+        perror("bind failed");
+        exit(EXIT_FAILURE);
+    }
+
+    if (listen(server_fd, 5) < 0) {
+        perror("listen");
+        exit(EXIT_FAILURE);
+    }
+
+    printf("TCP Multi-Connection Server listening on port %d...\n", PORT);
+    printf("Waiting for %d connections to transfer total %d MB...\n", EXPECTED_CONNECTIONS, TOTAL_TARGET_MB);
+
+    pthread_t threads[EXPECTED_CONNECTIONS];
+    int t_count = 0;
+
+    while (t_count < EXPECTED_CONNECTIONS) {
+        if ((new_socket = accept(server_fd, (struct sockaddr *)&address, (socklen_t*)&addrlen)) < 0) {
+            perror("accept");
+            exit(EXIT_FAILURE);
+        }
+
+        if (first_connect) {
+            clock_gettime(CLOCK_MONOTONIC, &start_time);
+            first_connect = 0;
+            printf("First connection received. Timer started.\n");
+        }
+
+        int *new_sock = malloc(1);
+        *new_sock = new_socket;
+        
+        if (pthread_create(&threads[t_count], NULL, handle_client, (void*)new_sock) < 0) {
+            perror("could not create thread");
+            return 1;
+        }
+        t_count++;
+    }
+
+    // Wait for all threads to finish
+    for (int i = 0; i < EXPECTED_CONNECTIONS; i++) {
+        pthread_join(threads[i], NULL);
+    }
+
+    clock_gettime(CLOCK_MONOTONIC, &end_time);
+
+    double time_taken = (end_time.tv_sec - start_time.tv_sec) + (end_time.tv_nsec - start_time.tv_nsec) / 1e9;
+    double mb = global_bytes_received / (1024.0 * 1024.0);
+    double throughput = mb / time_taken;
+
+    printf("\nTest Finished:\n");
+    printf("Total Connections: %d\n", connections_handled);
+    printf("Total Data Received: %.2f MB\n", mb);
+    printf("Time Taken: %.2f seconds\n", time_taken);
+    printf("Total Throughput: %.2f MB/s\n", throughput);
+
+    close(server_fd);
+    return 0;
+}